Edwin Diaz Is So Good It Scares Me

The Mariners once hoped that Edwin Diaz would develop into a really, really good starter. Instead, the Mariners decided to speed up the process and convert Edwin Diaz into a reliever. This statement isn’t entirely true, because the move wasn’t made solely to speed the process of Edwin Diaz, prospect, up. The conversion was made because the organization didn’t feel Diaz had a third pitch. And it’s true. Edwin Diaz does not have a third pitch. Just recently has Edwin Diaz found his second pitch, his slider. Newly departed former Mariner Joaquin Benoit taught him his slider. Diaz had a slider, and then about a week or so into his first stint in the major leagues, Benoit showed Diaz a new grip.

“The other one doesn’t break a lot,” Diaz said. “They show me a new grip, I start practicing, playing catch and then I throw in the game and now everybody talks about my slider.”

Unfortunately for Benoit, Diaz may be one of many reasons Benoit is now a former Mariner. Who knows how effective Diaz would have been with his previous slider grip, but with his new one, he’s been one of the most dominant relievers in baseball. Of pitchers with at least 20 innings pitched, Diaz:

  1. Has the highest K/9 in baseball at 17.38. (Next highest: 15.92. A huge difference.)
  2. A 1.86 ERA, good for top 15 in the MLB.
  3. A 1.38 xFIP (an ERA predictor), the 3rd best in all of baseball.
  4. A 45.2% K%. Good for best in all of baseball. 

Bottom line, Edwin Diaz has been flat out dominant. He’s struck out virtually two out of three batters per inning, on average, and apart from one run on August 3rd, hasn’t given up a run since July 6th. Diaz’s FIP/xFIP say that Diaz has possibly pitched even better than his ERA currently says he has. On the flip side, there are some peripherals that say something’s got to give.

Diaz’s BABIP (Batting Average on Balls In Play) currently stands at .444. Now that is awfully high. A typical pitcher’s BABIP will typically hover around .300. Now Edwin Diaz is certainly not your typical pitcher, but .144 or so away from the league average is quite a difference. In fact, Edwin Diaz’s BABIP is actually the highest in baseball (minimum 20 innings). The other three pitchers whose BABIPs are .400 or higher own ERAs of 5.13, 9.10, and 5.63. You should expect Diaz’s BABIP to eventually fall into the .300s, which means less opponents should be getting on-base with the balls they are putting into play.

Another rather simple metric that predicts some regression towards the mean is LOB% (Left on Base Percentage). Diaz’s LOB% is 94.7%,with only five pitchers (including Vidal Nuno!) having a higher LOB%. The league average is typically around 70%. However, high strikeout pitchers generally have better control over their LOB%. Edwin Diaz is a high strikeout pitcher, which probably says this is mostly extraneous. Of course Diaz is leaving runners on base, you say, he’s striking motherf*ckers out!

The last peripheral is Edwin Diaz’s HR/FB (Home Run to Fly Ball) rate. Diaz currently holds a HR/FB rate of 17.6% which is actually really bad. Usually when you hear a player has a statistic that is bad, that’s, well, bad. In this case, Diaz has an inflated HR/FB rate, and you can expect that rate to fall, especially when you factor in the skill level of Diaz. Since a league average HR/FB% is about 10%, you can maybe say that Edwin Diaz has gotten a bit unlucky with his home runs. The sample size is small (3 home runs in just 29 innings) so it’s not as easy to say if he’s been unlucky or not.

If we are to say that Edwin Diaz should have two home runs instead of, say, three, then Diaz’s BABIP would lower from .444 to a lower number that I do not want to calculate. This is because home runs do not factor into the BABIP formula.

So what does this all mean? Well, rhetorical question, this means that Edwin Diaz has been really really good, and he will continue to be really really good. Diaz is averaging 97 mph with his fastball and maxing out in the 100s. He’s throwing a slider with ridiculous movement that he throws 95 miles per hour. You never have, and you never will hit this kid.

And that brings me to this: Edwin is so good that it scares me. That was the title of this article, and also my initial point. But I will flip it this way: I have so many times been hurt by closers with wicked stuff that it’s almost hard to get attached to yet another. I legitimately feel that Sugar is going to be a force to be reckoned with for years to come, but we’ve felt that about relievers before. They’re unpredictable and they’re volatile. Tom Wilhelmsen was once our sweetheart. He’s still our sweetheart, but more in the way that your grandpa is really jaded and kind of racist. Not… that… Bartender is racist? Pitchers can be elite and fall off the face of the earth. I’ve seen it before and I’ll see it again. With Diaz in his current form, I doubt he will ever fall off.

Teams adapt, hitters adapt, and pitchers adapt. Maybe teams will learn to lay off the wicked slider. Maybe Diaz forgets how to locate. Maybe Diaz adapts in the wrong way. Things happen, and we don’t know the things that will happen. All we know are the things that are now and the things that we can predict will happen. I predict that Diaz will be lights out for the foreseeable future just like I predict Dave Sims will continue to create bad nicknames for players.

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